1. Field of the Invention
This invention relates to an electron collector for an electron beam tube, in particular a high performance transit tube, comprising a hollow collector member for receiving the beam electrons, which is surrounded by a metallic cooling sleeve that is grounded during operation of the tube and which is insulated from the same electrically for an operating potential which differs from the ground potential.
2. Description of the Prior Art
In a collector which is biased with respect to ground, for example a so-called "depressed collector" in transit time tubes, it is important that the collector be electrically insulated from its surrounding cooling sleeve in such a way that the loss connected therewith in respect of heat diffusion remains as low as possible. Generally, ceramic distance spacers are used as heat conducting insulating paths. For example, a ceramic sleeve may be soldered with the collector and the cooling sleeve as an insulator, as set forth in U.S. Pat. No. 3,471,739. Due to the different heat expansion coefficients of the soldered parts, however, during the heating of the tube thermal displacements occur during operation which can lead to the formation of cracks in the solder, and even to the breaking of the ceramic. Consequently, an apart from the fact that the ceramic is alreadly only as adequate a heat conductor as it is an electrical insulator, during the course of time unpredictable breaks in the heat transport capacity and locally very high temperature gradients occur which considerably reduce the performance and durability of the tube.
In order to meet such difficulties, it has been attempted to stack ceramic rings in a metal ceramic compound one after the other as a distance element between collector and sleeve metal ribs, whereby the ribs contact alternately either only the sleeve or only the collector. This type of structure is disclosed in U.S. Pat. No. 3,662,212. As a parallel hereto, a way has been found to support distance elements in recesses of the collector as well as the sleeve wall impressed thereon. This type of structure is disclosed in U.S. Pat. No. 3,679,929. All of these suggestions, however, require increased production efforts and costs, and do not lead to a long term satisfactory discharge condition.